Self-lubricating bearing for underbody automotive applications

ABSTRACT

A self-lubricating bearing and more particularly to a self-lubricated bearing which includes a race and a bearing element forming two mating bearing surfaces. For applications in which the bearing may be subjected to environmental conditions that could result in corrosion, one bearing surface may be formed from a corrosion resistant metal, such as stainless steel, while the mating bearing surface is homogeneously formed with the bearing element from a composite material which includes PFTE or Teflon. By homogeneously forming the bearing element from a composite material which includes Teflon, wear of the bearing element will not effect lubrication of the bearing.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field of the Invention

[0002] The present invention relates to a self-lubricated bearing andmore particularly to a self-lubricating radial bearing suitable for usein automotive underbody applications.

[0003] 2. Description of the Prior Art

[0004] Various of types of bearings are known in the art, for example,radial bearings are known for coupling a rotating element to astationery member to provide free and unrestricted rotation of therotating element relative to the stationery member. In order to preventundue wear, bearings are normally configured with provision forlubrication. As such, bearings normally include a cavity for holding alubricating material. An example of such a bearing is disclosed in U.S.Pat. No. 5,836,702. Lubricated bearings are either provided with afitting for replacing lubrication from an external source or provided ina sealed cavity. Sealed bearings are not suitable in many automotiveapplications due to the anticipated operation of the bearing over thewarranty life of the bearing. In particular, lubricants and sealedbearings lose their lubrication properties over time. Thus, forapplications where the number of bearing operations is expected toexceed the lubricant life, bearings are known which include provisionsfor external fittings to enable the lubricant within the bearings to bereplaced. An example of such a bearing is disclosed in U.S. Pat. No.5,791,787.

[0005] In other applications, bearings are used in relativelyinaccessible locations. Such bearings are configured as self-lubricatingbearings. Examples of such self-lubricating bearings are disclosed inU.S. Pat. Nos. 4,575,145; 5,219,231; 5,265,965; 5,273,369; 5,885,006 and5,056,938. In general, self-lubricating bearings include mating bearingsurfaces in which one bearing surface is formed from a metal and theother mating bearing surface is coated with Teflon also known as(polytetrafluorethylene or PFTE). Unfortunately, such Teflon coatingsare subject to wear and as a consequence could result in loss oflubrication surface after extended wear, eventually leading to acatastrophic failure of the bearing. Thus, there is a need for aself-lubricated bearing for use in extended use applications.

SUMMARY OF THE INVENTION

[0006] Briefly, the present invention relates to a self-lubricatingbearing and more particularly to a self-lubricated bearing whichincludes a race and a bearing element forming two mating bearingsurfaces. For applications in which the bearing may be subjected toenvironmental conditions that could result in corrosion, one bearingsurface may be formed from a corrosion resistant metal, such asstainless steel, while the mating bearing surface is homogeneouslyformed with the bearing element from a composite material which includesPFTE or Teflon. By homogeneously forming the bearing element from acomposite material which includes Teflon, wear of the bearing elementwill not effect lubrication of the bearing.

DESCRIPTION OF THE DRAWINGS

[0007] These and other advantages of the present invention will bereadily understood with reference to the following specification andattached drawing wherein:

[0008]FIG. 1 is an exploded perspective view of a rotary position sensorformed with a housing in accordance with the present invention, shownwithout a printed circuit board, magnetic flux responsive element andflux concentrators.

[0009]FIG. 2 is a top view of the rotary position sensor illustrated inFIG. 1.

[0010]FIG. 3 is a sectional view along line 3-3 of the FIG. 2.

[0011]FIG. 4 is similar to FIG. 1 illustrating the rotary positionsensor in accordance with the present invention partially assembled withthe printed circuit board, magnetic flux responsive element and fluxconcentrators shown exploded.

[0012]FIG. 5 is a bottom view of the rotary position sensor illustratedin FIG. 4.

[0013]FIG. 6 is a sectional view along the line 6-6 of FIG. 5.

[0014]FIG. 7 is a bottom view of a molded housing which forms a part ofthe present invention.

[0015]FIG. 8 is a top view of the molded housing illustrated in FIG. 7.

[0016]FIG. 9 is a sectional view along the line 9-9 of FIG. 7.

[0017]FIG. 10 is a detail of a portion of the housing illustrated inFIG. 7.

[0018]FIG. 11A and 11B are perspective views of a rotor plate inaccordance with the present invention.

[0019]FIG. 12 is a top view of the rotor plate illustrated in FIGS. 11Aand 11B.

[0020]FIG. 13 is a sectional view along line 13-13 of FIG. 12.

[0021]FIG. 14 is a sectional view along line 14-14 of FIG. 12.

[0022]FIG. 15 is a detailed view of a portion of the rotor plateillustrated in FIG. 14.

[0023]FIG. 16 is a detailed view of a portion of the rotor plateillustrated in FIG. 12.

[0024]FIGS. 17A and 17B are perspective views of a drive arm assembly inaccordance with the present invention.

[0025]FIG. 18 is a side view of the drive arm assembly illustrated inFIGS. 17A and 17B.

[0026]FIG. 19 is a bottom view of the drive arm assembly illustrated inFIG. 18.

[0027]FIG. 20 is a sectional view along line 20-20 of FIG. 19.

[0028]FIG. 21 is a top view of the drive arm assembly illustrated inFIG. 18.

[0029]FIG. 22A-22C illustrate the magnetic circuit for various positionsof the magnet relative to the magnetic flux responsive element.

[0030]FIG. 23 is a plan view of a race which forms a portion of theself-lubricating bearing in accordance with the present invention.

[0031]FIG. 24 is a sectional view along line 24-24 of FIG. 23.

DETAILED DESCRIPTION

[0032] The present invention relates to a self-lubricating bearingconfigured, for example, as a radial bearing, which includes a race andbearing element. The race is illustrated in FIGS. 23 and 24 while thebearing element is illustrated in FIGS. 17A-22. An important aspect ofthe invention is that the bearing surfaces on the race and the bearingelement are configured to provide self-lubrication. Unlikeself-lubricating bearings disclosed in the prior art, the race and thebearing element are formed from homogeneous materials. Accordingly, thelubrication effect provided at the bearing surfaces will not bediminished as the mating bearing surfaces wear.

[0033] Although the radial bearing in accordance with the presentinvention is described in terms of a rotary position sensor for use inan automobile underbody application, the principles of the presentinvention are applicable to virtually any type of bearing. FIGS. 23 and24 illustrate the race while FIGS. 17A-22 illustrate the bearing elementconfigured as a drive arm assembly for a rotary position sensor asgenerally illustrated in FIGS. 1-22.

[0034] The present invention relates to a self-lubricating bearingsuitable for use in automotive underbody applications. Theself-lubricated bearing in accordance with the present inventionincludes a race 15 (FIGS. 23 and 24) and a bearing element 24. As shownand as will be discussed in more detail below, the bearing element 24includes an axial annular bearing surface 16 (FIG. 18) and a radialbearing surface 17. These bearing surfaces 16 and 17 are adapted to matewithin an interior bearing surface 18 (FIG. 22) formed on the interiorsurface of the race 15. In particular, the annular axial bearing surface16 (FIG. 18) on the bearing element or drive arm assembly 24 is adaptedto mate with the inner surface 18 (FIG. 23) of the race 15. Similarly,the bearing surface 17 of the bearing element 24 in a radial plane isadapted to mate with one or the other of the radial surfaces 19, 21(FIG. 23) of the race 15.

[0035] In general, the race 15 may be formed from metal. In applicationswhere the bearing is subject to corrosive environments, such as in anautomobile underbody environment, the race may be formed from acorrosion resistant metal such as ATSM 304 stainless steel with a finefinish.

[0036] The bearing element or drive arm 24 (FIG. 18) may behomogeneously formed from a polymer, such as composite plastic materialthat is blended with PFTE or Teflon. The plastic material may be athermoset or thermoplastic material, such as glass-filled 6-12 nylonwith, for example, 15% Teflon.

[0037] The bearing provides a metal-to-polymer bearing that isself-lubricating in which the Teflon migrates to the surface as thecomponents wear for the life of the bearing. As such, unlike theself-lubricating bearings in the prior art, wear of the mating surfacesof the bearing components does not diminish the lubrication effect ofthe self-lubricating bearing.

[0038] The following is an exemplary application of the self-lubricatingradial bearing utilized in a rotary position sensor application for usein a automotive underbody application. In this application, the bearingrace 15 is disposed within a molded housing 22 for providing bearingsurfaces for a rotatable bearing element or drive arm 24 as best shownin FIGS. 6 and 9.

[0039] Turning to FIGS. 1-22, the rotary position sensor, generallyidentified with the reference numeral 20, includes a molded housing 22,a drive arm assembly 24 and a rotor plate 26.

[0040] A lever arm assembly 28, which does not form part of the presentinvention, may be attached to the drive arm assembly 24 by a suitablefastener 30. The lever arm 28 is adapted to be mechanically coupled toan external device whose rotational movement is to be sensed.

[0041] The rotor plate 26, shown best in FIGS. 13-16, is formed with arotor cavity 32 for receiving a pair of flux concentrators 34, 35 (FIGS.4 and 22A-22C) and a magnetic responsive element 36, such as a Halleffect IC and an optional flux shunt if required. The flux concentrators34, 35 may be formed from a soft magnetic material with semi-circularcross-section and disposed within the rotor cavity 32 along with themagnetic flux responsive element 36. The flux concentrators 34, 35 aredisposed on opposing sides of the magnetic flux responsive element 36and disposed within the rotor cavity 32 (FIGS. 22A-22C). As shown inFIGS. 4-16, a printed circuit board 38 may be used to provide anelectrical connection between the magnetic flux responsive element 36and a plurality of terminals 40 (FIG. 4) disposed within the mainhousing 22.

[0042] As best shown in FIGS. 1 and 7-10, the molded housing 22 isprovided with a central aperture 42 (FIG. 7) for receiving the drive armassembly 24. As shown in FIG. 3, one end 44 of the molded housing 22 isformed with a reduced diameter portion 46 which contacts an annularshoulder 49 (FIG. 20) on the drive arm assembly 24 to form a stop andlimit axial movement of the drive arm assembly 24 in a direction of thearrow 47. The other end 48 of the molded housing 22 is formed withannular stepped surfaces, generally identified with the referencenumeral 50 (FIGS. 7-9). The rotor plate 26 is formed with correspondingannular stepped surfaces 52 (FIGS. 3, 6, 13 and 14) that are adapted tomate with the stepped surfaces 50 formed in the molded housing 22 asbest shown in FIGS. 3 and 6. The stepped surfaces 50 and 52 may beultrasonically welded together.

[0043] The details of the molded housing 22 are illustrated in FIGS.7-10. As shown in FIGS. 7 and 10, the aperture 42 is formed with aradial slot 56. The radial slot 56 is used to provide radial orientationof the rotor plate 26 relative to molded housing 22. In particular, therotor plate 26 is provided with a radial tab 58 (FIG. 12). The radialtab 58 is adapted to be received in the radial slot 56 (FIG. 10) toprovide radial registration of the rotor plate 26 relative to the moldedhousing 22.

[0044] As shown in FIG. 13, the rotor plate 26 is provided with anaxially extending sleeve portion 60. The sleeve portion 60 is adapted tobe received in a hollow cavity 62 (FIG. 20) formed in the drive armassembly 24. As shown in FIGS. 12 and 14-16, the sleeve portion 60 ofthe rotor plate 26 is formed with a hollow cavity 62 (FIG. 13) forreceiving one or more flux concentrators 34, 35 (FIG. 4) and a magneticflux responsive element 36 and flux shunt, if required. As shown inFIGS. 3 and 6, such a configuration allows the drive arm assembly 24 torotate relative to the cavity 62 and thus also rotate relative to theflux concentrators 34, 35 and the magnetic flux responsive element 36(FIG. 4) and flux shunt, if used.

[0045] As illustrated best in FIG. 20, the drive arm assembly 24includes a generally circular magnet 64 and shunt ring 66. As shown, theshunt ring 66 circumscribes the circular magnet 64. When the rotor plate26 and drive arm assembly 24 are assembled to the molded housing 22, asgenerally shown in FIGS. 3 and 6, the circular magnet 64 as well as theshunt ring 66 are axially aligned with a portion of the annular cavityformed in the axially extending portion 60 of the rotor plate 26 whichresults in the annular magnet 64 and shunt ring 66 being axially alignedwith magnet 64 and shunt ring 66, as best shown in FIG. 6. Accordingly,rotation of the drive arm assembly 24 results in radial displacement ofthe circular magnet 64 relative to fixed position of the magnetic fluxresponsive element 36 and flux concentrators 34, as shown in FIGS.22A-22C and generate a signal representative thereof.

[0046] The configuration of the magnet 64 illustrated in FIGS. 22A-22Cis merely exemplary. In particular, the magnet 64 is shown as adiametrically charged magnet. The principles of the present inventionare applicable to all magnet configurations including radially chargedmagnets (not shown).

[0047] Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings. Thus, it is tobe understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedabove.

What is claimed and desired to be covered by a Letters Patent is asfollows:
 1. A self-lubricating bearing comprising: a metal race; and acomposite bearing element formed from a polymer blended with Teflon. 2.The self-lubricating bearing as recited in claim 1, wherein saidself-lubricating bearing is configured as a radial bearing.
 3. Theself-lubricating bearing as recited in claim 2, wherein said metal raceis formed from a corrosion resistant material.
 4. The self-lubricatingbearing as recited in claim 3, wherein said corrosion resistant metal isstainless steel.
 5. The self-lubricating bearing as recited in claim 4,wherein said composite material is formed from a thermoset materialblended with Teflon.
 6. The self-lubricating bearing as recited in claim4, wherein said composite material is formed from a thermoplasticmaterial blended with Teflon.
 7. The self-lubricating bearing as recitedin claim 4, wherein said composite material is formed from a nylonmaterial blended with Teflon.
 8. The self-lubricating bearing as recitedin claim 7, wherein said nylon material is 6-12 nylon.
 9. Theself-lubricating bearing as recited in claim 7, wherein said nylonmaterial is glass filled.
 10. The self-lubricating bearing as recited inclaim 9, wherein said nylon material is 6-12 nylon, glass filled andblended with Teflon.
 11. The self-lubricating bearing as recited inclaim 10, wherein said composite material is blended with about 15%Teflon.
 12. The self-lubricating bearing as recited in claim 1, whereinsaid bearing is formed with a housing with a central aperture and saidrace is disposed in said central aperture.
 13. A rotary position sensorcomprising: a housing formed from a non-magnetic material having acentral aperture; a metallic race disposed in said central aperture; adrive arm assembly formed from a composite material which includesTeflon and includes a generally circular magnet and a shut ring,configured with a rotor cavity; and a magnetic flux responsive elementand one or more flux concentrators adapted to be rigidly disposed withinsaid rotor cavity and configured such that said magnet and shunt ringrotate with respect to said housing and said magnetic flux responsiveelement.
 14. The rotary position sensor as recited in claim 13, whereinsaid metallic race is formed from a corrosion resistant metal.
 15. Therotary position sensor as recited in claim 14, wherein said corrosionresistant material is stainless steel.
 16. The rotary position sensor asrecited in claim 13, wherein said composite material is formed from athermoset material blended with Teflon.
 17. The rotary position sensoras recited in claim 13, wherein said composite material is formed from athermoplastic material blended with Teflon.
 18. The rotary positionsensor as recited in claim 13, wherein said composite material is formedfrom a nylon material.
 19. The rotary position sensor as recited inclaim 18, wherein said nylon material is glass filled 6-12 nylon. 20.The rotary position sensor as recited in claim 19, wherein saidcomposite material is blended with 15% Teflon.